Summary
The present study showed that male, high BMI, prolonged surgery, and articular cartilage damage were identified as risk factors of IFP fibrosis 3 months after ACLR. IFP fibrosis was an independent risk factor of lower patient-reported outcomes and extension deficit at 1 year postoperatively. These findings could offer valuable information for surgeons to avoid IFP fibrosis at the time of surgery.
Abstract
Background
Infra-patella fat pad (IFP) fibrosis is a widely known complication after ACLR. IFP fibrosis has been shown to cause AKP and consequently can lead to delayed rehabilitation. Moreover, patients with more severe IFP fibrosis after ACLR have been reported to have poorer short-term clinical outcomes.
Purpose
To examine the risk factors of IFP fibrosis and associations between the degree of IFP fibrosis and clinical outcomes in patients with ACLR.
Methods
Patients who underwent primary double-bundle ACLR using autologous hamstring tendons between 2014 and 2019 were divided into the mild fibrosis group (M group) and severe fibrosis group (S group), based on IFP fibrosis scoring (grades 0–5) on magnetic resonance imaging at 3 months postoperatively. Patient demographics (age, sex, BMI, and pre-injury Tegner activity scale), operative findings (operation time, meniscus injury, and cartilage injury) and clinical outcomes (ROM, extension muscle strength, post-operative Tegner activity scale, IKDC subjective score, and KOOS score) at 1 year postoperatively were compared between groups. Statistical analyses were performed using STATA 15.0 software. The Student’s t-test or chi-square test were used to compare between two groups. Multiple linear regression analyses were conducted to assess the strength of the relationship between clinical outcomes at 1 year postoperatively and seven predictor variables, including IFP fibrosis, patient demographics and operative findings. For all analyses, p-values <0.05 were considered as statistically significant.
Results
In total, 97 patients were included (S group: n=21; M group: n=76). There were significantly more males (57.1% vs 30.3%; p=0.036), higher BMI (25.1 vs 23.0; p=0.004), longer operation times (168.0 min vs 135.4 min; p=0.031), and more cartilage injuries evaluated by ICRS classification (grades 0–1 considered as no cartilage damage and grades 2–4 as cartilage injuries) (47.6% vs 23.7%; p=0.030) in the S group than in the M group. International Knee Documentation Committee (IKDC) subjective scores (83.1 vs 88.5; p=0.040), and Knee Injury and Osteoarthritis Outcome Score (KOOS) symptoms (87.2 vs 93.4; p=0.009) and quality of life (QOL) values (76.8 vs 86.2; p=0.026) were significantly lower in the S group than in the M group. The range of motion was significantly worse on both extension (0.0 vs 1.8; p<0.001) and flexion (145.9 vs 150.4; p=0.002) in the S group than in the M group. Multiple regression analysis revealed IFP fibrosis as an independent factor affecting the IKDC subjective score (ß = -6.05, p=0.037), KOOS-symptom subscore (ß = -5.24, p=0.037), and extension angle (ß = -1.40, p=0.002).
Conclusions
Male sex, high BMI, prolonged surgery, and articular cartilage damage are risk factors for IFP fibrosis after ACLR. IFP fibrosis affects the range of motion and subjective patient evaluations including the IKDC subjective score, KOOS symptoms and QOL subscore at 1 year postoperatively. IFP fibrosis should be considered as a predictor of slow recovery and worse short-term subjective outcomes in patients who undergo ACLR. Surgeons should take care to avoid IFP damage and prolonged operation time during ACLR surgery, especially when operating on male patients with cartilage injuries.